PURPOSE: To perform self-steering of tyre reliably by moving a roller provided in a roller bracket under steering while resetting to the normal position when travelling straight.

CONSTITUTION: A roller 17 is set between roller arms 14, 14 and a chamber rod 24 is fully stretched by the air pressure passing through an air piping of an air- chamber 23 to ensure centering. When turning, said roller 17 will move on the inclined face of roller arm 14 to the right while the chamber rod 24 is pushing the roller 17 upward through the air pressure but pushed downward through rotation of roller 17. The roller arm 14 will rotate through the shaft 22 to increase the inclination angle thus to contain the roller 17 smoothly in the central recess between the roller arms 14, 14.